Anthroplasty component

ABSTRACT

An arthroplasty component is positioned relative to a bone by engaging a first side of the bone with a first tab on the arthroplasty component. Thereafter, the arthroplasty component is pivoted about a location where the first tab engages the first side of the bone. A second tab on the arthroplasty component is moved along a second side of the bone while the arthroplasty component is pivoted about the location where the first tab engages the first side of the bone. A tray portion of the arthroplasty component is positioned over a portion of the bone disposed between the first and second sides of the bone while the arthroplasty component is pivoted about the location where the first tab engages the first side of the bone. In one embodiment of the invention, a keel is moved into the bone at a location between the sides of the bone while the arthroplasty component is pivoted about the location where the first tab engages the first side of the bone. A fastener may be moved through the second tab, a portion of the bone and into the keel portion of the arthroplasty component to retain the arthroplasty component against movement relative to the bone.

This is a divisional of application Ser. No. 07/926,481 filed on Aug. 6,1992, now U.S. Pat. No. 5,344,458.

BACKGROUND OF THE INVENTION

The present invention relates to an arthroplasty component. Moreparticularly, the present invention relates to an arthroplasty componentfor capping a bone, such as a glenoid component for use in shoulderarthroplasty.

DESCRIPTION OF THE PRIOR ART

Arthroplasty is the reshaping or reconstructing of a diseased or damagedjoint. The procedure may require use of artificial joint components toreplace natural joint portions. Some natural joint portions are replacedwith components having a tray portion with an articulating surface forengagement with a head portion of a long bone (or its replacement). Suchjoint portions include the tibia and the glenoid process of the scapula(or the "glenoid bone").

The glenoid bone is funnel-shaped, having an outer (distal) end surfacewhich is the articulating surface, and an outer side surface extendingproximally from the outer end surface. A typical glenoid component isfixed to the glenoid bone using bone cement and an intramedullary keel.This type of fixation often fails, because the intramedullary keel islocated in soft cancellous bone rather than hard cortical bone. Thistype of fixation is also difficult and traumatic, because of the need todrill an opening for the intramedullary keel in a direction generallynormal to the articulating surface of the glenoid bone. Such drillingrequires a large exposure of the joint, and complex and difficult to usetools.

It would thus be desirable to have a glenoid component which can befixed to the glenoid bone in a different manner, and preferably withoutthe need for bone cement. It is desirable to avoid bone cement becausethe body may react to the cement. There is a higher incidence ofinfection when bone cement is used. Also, bone cement can fatigue andbreak. Particles of bone cement can break off and cause furtherdestruction in the joint. Further, fractures can propagate easily inbone cement, so that a small area of damage to a layer of bone cementwill result in total failure of the layer of bone cement.

SUMMARY OF THE INVENTION

The present invention is an arthroplasty component for affixation to abone having an outer end surface and an outer side surface. Thecomponent has a tray portion for overlying an end surface of the bone.The tray portion has portions extending from the tray portion forengaging the outer side surface of the bone to block movement of thetray portion in a first direction on the bone.

In a preferred embodiment, the present invention is a glenoid componentfor affixation to a glenoid bone having an outer end surface and anouter side surface, the glenoid component being engageable by a humeralpart. The glenoid component includes a tray portion for overlying theaxial end surface or articulating surface of the glenoid bone. The trayportion has an outer major side surface for engagement with the humeralpart, an inner major side surface for engagement with the outer endsurface of the glenoid bone, and an outer periphery. A first tab extendsaxially from the outer periphery of the tray portion for engagement withthe outer side surface of the glenoid bone. A second tab extends axiallyfrom the outer periphery of the tray portion for engagement with theouter side surface of the glenoid bone. The tabs hold the glenoidcomponent in place on the glenoid bone.

The glenoid component may also include fastener means such as a screwengageable with one of the first and second tabs and extensibletransversely through the outer side surface of the glenoid bone forsecuring the glenoid component to the glenoid bone.

The glenoid component of the present invention is highly advantageous ascompared to typical glenoid components which use cement and anintramedullary keel. The present glenoid component is easier to implantbecause it uses an anterior fastener in place of the standardintramedullary keel. Less soft tissue damage occurs because of thesimpler exposure required. Minimal bone resection is required, as nointramedullary opening must be formed. The component has improvedstability in shear, torsion, and anterior-posterior lift off.

Further, because of the secure fixation resulting from the engagement ofthe tabs on the hard cortical material of the glenoid bone, there isusually no need to cement the glenoid component onto the glenoid bone.This allows for decreased glenoid offset, which is advantageous, andalso for the use of bone ingrowth material. If bone cement is used,texturing on the inner major side surface of the component limitspropagation of cracks in the bone cement. The optional screw fixationwhich may extend into the anterior bone cortex or may be transcorticalprovides even further stability. There is no need to have a 90° angleglenoid screw, as is sometimes used to secure a glenoid component. Thereis no need to use angled burrs or reamers to drill central openings.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present invention will becomeapparent to one skilled in the art to which the present inventionrelates upon consideration of the following description of the inventionwith reference to the accompanying drawings, wherein:

FIG. 1 is a sectional view, taken along line 1--1 of FIG. 3, of aglenoid component for capping a glenoid bone in shoulder arthroplasty;

FIG. 2 is a top plan view of the glenoid component of FIG. 1;

FIG. 3 is a bottom plan view of the glenoid component of FIG. 1;

FIG. 4 is a schematic illustration of a glenoid bone prior to capping;

FIG. 5 is a schematic illustration of the glenoid bone of FIG. 4 withthe glenoid component of FIG. 1 in a partially inserted position;

FIG. 6 is a schematic illustration of the glenoid bone of FIG. 4 aftercapping with the glenoid component of FIG. 1;

FIG. 7 is a fragmentary view of a glenoid component having a modifiedanterior tab;

FIG. 8 illustrates a glenoid component modified by the addition of asolid central keel;

FIG. 9 illustrates a glenoid component modified by the addition of acentral keel having a tapered opening therein;

FIG. 10 is an elevational view of a screw for use with the glenoidcomponent of FIG. 9;

FIG. 11 is an assembly view of the parts of FIGS. 9 and 10;

FIG. 12 is a bottom plan view of a tibial component for capping a tibiain knee arthroplasty;

FIG. 13 is an elevational view of the tibial component of FIG. 12;

FIG. 14 is a bottom plan view of a patellar implant in accordance withthe present invention;

FIG. 15 is an elevational view of the patellar implant of FIG. 14;

FIG. 16 is an elevational view of a reinforced implant;

FIG. 17 is a sectional view taken along line 17--17 of FIG. 16;

FIG. 18 is a side elevational view of another tibial tray in accordancewith the present invention;

FIG. 19 is a front elevational view of the tibial tray of FIG. 18;

FIG. 20 is an end view of another bone screw in accordance with thepresent invention;

FIG. 21 is an elevational view of the bone screw of FIG. 20;

FIG. 22 is an end view of a third bone screw in accordance with thepresent invention; and

FIG. 23 is an elevational view of the bone screw of FIG. 22.

DESCRIPTION OF PREFERRED EMBODIMENT

The present invention relates to a joint component for use inarthroplasty. The present invention is applicable to various jointcomponent constructions. As representative of the present invention,FIG. 1 illustrates a glenoid component 10. The glenoid component 10includes a metal base 12 and a plastic insert 14. The metal base 12 hasa lower major side surface 16 for placement adjacent to the articulatingsurface of a glenoid bone (not shown). The plastic insert 14 has aconcave upper major side surface 18 for articulation with a humeral partof the glenohumeral joint when the glenoid component 10 caps the glenoidbone.

The metal base 12 includes a tray portion 20 with an outer periphery 30(FIG. 2) which is the outer periphery of the glenoid component 10. Themetal base 12 has an upper peripheral portion 32, an anterior peripheralportion 34, a lower peripheral portion 36, and a posterior peripheralportion 38. The tray portion 20 of the glenoid component 10 has an uppermajor side surface 40.

The plastic insert 14 is received in a cut-out 42 in the upper surfaceof the base tray portion 20. The cut-out 42 is sized to snugly receivethe plastic insert 14, in a known manner. The cut-out 42 is defined byan edge surface 70 and a major side surface 72. The plastic insert 14has a lower side surface 74 in engagement with the surface 72 of themetal base 12, and an outer side surface 76 in engagement with the edgesurface 70 of the cut-out 42 in the metal base 12.

The metal base 12 has three integral tabs projecting proximally (down asviewed in FIG. 1) from the tray portion 20. These include an anteriortab 22, an upper posterior tab 24, and a lower posterior tab 26.

The anterior tab 22 (FIG. 1) projects downwardly as viewed in FIG. 1from the anterior peripheral portion 34 of the tray portion 20 of themetal base 12. The anterior tab 22 extends generally normal to the trayportion 20 of the metal base 12, in a direction parallel to an axis 50of the glenoid component 10. The anterior tab 22 has an outer sidesurface 44, an inner side surface 46, and a lower side surface 48connecting the inner side surface and the outer side surface. A screwhole 52 extends at an angle through the anterior tab 22.

The lower posterior tab 26 (FIG. 3) is generally similar to the anteriortab 22. The lower posterior tab 26 projects downwardly as viewed in FIG.1 from the lower peripheral portion 36 of the tray 20. The lowerposterior tab 26 has an outer surface 54, an inner surface 56, and alower side surface 58 joining them.

The upper posterior tab 24 has a support portion 60 (FIG. 1) having aninner side surface 62 and an outer side surface 64. A hook portion 66extends transversely from the support portion 60 inwardly toward theanterior tab 22 in a direction transverse to the axis 50 of the glenoidcomponent 10. The hook portion 66 has a relatively sharp distal endportion 68 joined by a lower side surface 70 to the outer side surface64 of the support portion 60.

It should be noted that the anterior tab 22 and the posterior tabs 24and 26 can be located elsewhere on the periphery 30 of the glenoidcomponent 10. Further, the tabs 22, 24 and 26 may have different lengthsand/or configurations, so long as they serve the function of blockinglateral movement of the tray portion 20 by engagement with the outerside surface of the glenoid bone. The length of the anterior tab 22along the periphery of the glenoid component 10 is selected so as tosubstantially block movement of the tray portion 20 in a first directionrelative to the glenoid bone, when the anterior tab 22 engages an outerside surface of the glenoid bone. Similarly, the upper posterior tab 24and the lower posterior tab 26 are located and dimensioned so as tosubstantially block movement of the tray portion 20 of the glenoidcomponent 10 relative to the glenoid bone in a second direction. Theremay also be a different number of tabs provided, or even one tabextending partially or completely around the periphery 30 of the glenoidcomponent 10.

The lower major side surface 16 of the tray portion 20 includes anaxially outward web surface 80 (FIG. 3). The lower major side surface 16also includes a plurality of spherical surfaces 82 defining a pluralityof dimples 84 in the tray portion 20. In a preferred embodiment, thedimples 84 are two to three millimeters in diameter.

The glenoid component 10 is usable in capping a glenoid bone, such asthe glenoid bone 100 illustrated schematically in FIGS. 4-6. The glenoidbone 100 is funnel-shaped and has a neck portion 102 extending inwardlyfrom the end portion 104. The end portion 104 has an articulatingsurface 106 which may be cut back if desired to accommodate thethickness of the glenoid component 10. The glenoid bone has an anteriorouter side surface 108 and a posterior outer side surface 110.

FIGS. 5 and 6 illustrate the securing of the glenoid component 10 to theglenoid bone 100. After the joint is exposed anteriorly, the glenoidcomponent 10 is slid between the parts of the joint, from anterior toposterior, in a direction as indicated by the arrow 120. When theposterior tabs 24 and 26 of the glenoid component 10 are posterior tothe glenoid bone 100, the posterior tabs are slid proximally relative tothe glenoid bone 100 in a direction as indicated by the arrows 122.

The hook portion 66 of the upper posterior tab 24, with its end portion68, is engaged with the posterior outer side surface 110 of the glenoidbone 100 as shown in FIG. 5. The glenoid component 10 is then pivotedabout the hook portion 66, in the direction indicated by the arrow 124,from the position shown in FIG. 5 to the position shown in FIG. 6. Inthe position shown in FIG. 6, the lower major side surface 16 of theglenoid component 10 is adjacent to or in engagement with thearticulating surface 106 of the glenoid bone 100. The anterior tab 22 isin engagement with the anterior outer side surface 108 of the glenoidbone 100. The lower posterior tab 26 (not shown in FIGS. 4-6) is also inengagement with the posterior outer side surface 110 of the glenoid bone100.

A fastener, such as a screw 120, may then optionally be inserted throughthe screw hole 52 in the anterior tab 22 of the metal base 12. The screw120 engages in the hard cortical bone on the anterior portion of theglenoid bone 100. Alternatively, the fastener may extend across theglenoid bone 100 and terminate in the cortical bone on the posteriorside of the glenoid bone. Suitable holes may be drilled in the glenoidbone 100 to receive the fastener, as necessary. It is contemplated thata glenoid component in accordance with the present invention will likelybe fixed to the glenoid bone with a screw such as the screw 120.However, this may not in all cases be necessary, and so the presentinvention also contemplates capping with the tabs only, without aseparate fastener.

The tabs 22, 24 and 26 block both lateral and axial movement of the trayportion 20 of the glenoid component 10 relative to the glenoid bone 100.The anterior to posterior dimension of the glenoid bone 100 may beshortened, prior to capping, by resecting an anterior edge portion 112(FIG. 4) of the glenoid bone 100, so that the glenoid component 10 snapsinto position on the glenoid bone 100 and is retained snugly in positionthereon. It should be understood that the steps recited above forpositioning the glenoid component 10 or the glenoid bone 100 may andlikely will be varied, as the surgeon moves and works the glenoidcomponent into place on the glenoid bone, to the position shown in FIG.5 and then the position shown in FIG. 6.

The hook 66 on the posterior lip 24 provides a pivot point for mountingof the glenoid component 10 on the glenoid bone 100. The hook 66 alsoblocks axial outward movement of the glenoid component 10 from the bone100.

The tabs 22, 24 and 26 on the glenoid component 10 engage hard corticalbone material at the outer surface of the bone 100. The cortical bone isless likely to wear away and loosen the grip of the tabs on the bone,than is cancellous bone. Thus, the fixation obtained by the presentinvention is superior to that obtained by a central (intramedullary)keel which is in soft cancellous bone.

The anterior and posterior tabs 22, 24 and 26 engage the glenoid bone100 at locations spaced from the center of the bone. The tabs are thusworking through a longer lever arm to resist rotation of the glenoidcomponent 10 on the bone. For this reason also, the stability obtainedby the present invention is superior to that obtained by a central keel.

Because component fixation is obtained at the outer edges of the bonewith the present invention, no intramedullary screws are needed to affixthe component. This eliminates the possibility of metal screw headswearing on the under surface of a plastic insert, which is a known causeof component failure. It also eliminates the need for a thicker metalcomponent to accommodate the screw fixation. Any screw fixation in thepresent invention is obtained laterally through the outer side surfaceof the glenoid bone into hard cortical bone, which is clearly superior.

The metal base 12 of the glenoid component 10 is preferably titanium orcobalt chrome two to three millimeters thick. The plastic insert 14 ispreferably polyethylene or polyetheretherketone about three millimetersthick. Thus, the total thickness of the glenoid component is about fiveto six millimeters. This is in contrast to the normal glenoid componentwhich is eleven millimeters thick. The glenoid component of the presentinvention can be made thinner because no fixation need be obtained alongthe tray portion, fixation rather being obtained at the side of thebone.

FIG. 7 illustrates alternative configurations for an anterior tab 22a ofa glenoid component 10a. The anterior tab 22a may include a hook portion126 similar to the hook portion 66 (FIG. 1) of the posterior tab 24. Theanterior tab 22a may include a post 128 formed integrally with theanterior tab 22a, and extending inwardly from an inner side surface 130of the tab 22a to a pointed end portion 132. The post 128 could replacethe screw 120.

FIG. 8 illustrates another alternative configuration for a glenoidcomponent in accordance with the present invention. The glenoidcomponent 134 includes a metal base 136 with a plastic insert 138. Themetal base 136 has an anterior tab 140 and one or more posterior tabs142, which may have a hook portion 144. A small intramedullary keel 146is provided with a pointed distal end portion 148 extending along theaxis 150 of the glenoid component 134. Upon movement of the glenoidcomponent 134 into position on a glenoid bone, as illustrated in FIGS. 5and 6, the keel 146 embeds in the intramedullary bone to further assistin stabilizing the glenoid component 134 on the glenoid bone.

FIGS. 9-11 illustrate another embodiment of the present invention inwhich a transcortical screw 150 assists in securing a glenoid component152 to a glenoid bone. The glenoid component 152 has a metal base 154and a plastic insert 156. The base 154 has an anterior tab 156 with ascrew hole 158 extending therethrough. The screw hole 158 is countersunkat 160. The base 154 also has a posterior tab 162 with a hook portion164.

A central keel 166 extends axially from a tray portion 168 of the base154. The keel 166 has an anterior side surface 170 and a posterior sidesurface 172. A tapered opening 174 extends transversely through the keel166 from the anterior side surface 170 to the posterior side surface172. The opening 174 has a standard Morse taper.

The screw 150 (FIG. 10) has a head portion 175 for engagement with thecountersunk portion 160 of the screw hole 158. A tapered shank portion176 of the screw 150 is disposed intermediate a distal shank portion 178and a proximal shank portion 180 of the screw 150. The shank portion 176has a Morse taper matching that of the opening 174 in the keel 166 ofthe component 152. The screw 150 has a distal threaded portion 182adjacent the distal end 184 of the screw 150. A proximal threadedportion 186 is disposed on the proximal shank portion 180 adjacent thescrew head 154.

The glenoid component 152 is first placed over the glenoid bone (shownschematically in FIG. 11) as described above. A through hole is drilledfor the screw 150. The screw 150 is inserted through the screw hole 158in the anterior tab 156 of the glenoid component 152. The variousportions of the screw 150 are dimensioned so that, as the distal andproximal threaded portions 182 and 186 draw the screw head 175 snuglyinto engagement with the anterior tab 156, the tapered screw portion 176engages in the tapered opening 174 in the keel 166. The interlockingbetween the screw 150 and the keel 166 further aids in stability,especially rotational stability, of the glenoid component 152 on theglenoid bone. It should be noted that either the proximal threadedportion 186 or the distal threaded portion 186 may be omitted, and thatthey may have different thread pitches as desired. For example, thethread portion 182 is illustrated as having a finer pitch than thethreaded portion 186.

The screw 150 extends at an angle α relative to the plane of the glenoidcomponent 152. The angle α is selected so as to provide the minimumamount of lift off and the maximum amount of rotational stability, whilestill maintaining anterior exposure only and cortical rather thanmedullary fixation. This same angle is used with the screw 120 (FIG. 6)for holding the glenoid component 10 in place on the glenoid bone 100.The angle α is preferably about 10°.

The present invention is applicable to joints other than theglenohumeral joint. Other joints which have bones which may be capped inaccordance with the present invention include (without limitation) theknee, ankle, wrist, and hip (acetabulum). As an example, FIGS. 12 and 13illustrate a tibial tray 200 having an articulating surface 202 and alower major side surface 204. The lower major side surface 204 has aplurality of two millimeter diameter dimples or depressions 206. Aplurality of tabs 208 extend downwardly from the lower major sidesurface 204 of the tibial tray 200. The tabs 208 are engageable with anouter side surface of the tibia bone (not shown) to block movement ofthe tibial component 200 relative to the tibia. Fastener openings 210may be provided in the tabs 208 for optional screw fixation laterallythrough cortical bone of the tibia. The number, dimensions, andplacement of the tabs 208 may be selected to give best securing of thetibial tray 200 to the tibia.

Although the foregoing description has referenced cementlessinstallation of arthroplasty components, it is also contemplated thatbone cement may be used if desired by the surgeon. The texturing of thelower side surfaces of the illustrated components is useful in thisregard. Bone cement is applied between the end surface of the bone to becapped and the lower major side surface of the component. The bonecement flows mainly into the dimples or impressions on the lower sidesurface of the component, and also may form a thin layer on the websurface of the component. For example, the bone cement when appliedbetween the articulating surface 106 (FIG. 6) of the glenoid bone 100and the lower major side surface 16 of the glenoid component 10, wouldflow into the dimples 84, and possibly lie on the web surface 80. Thus,any cracks which would form in the bone cement would tend to propagateonly to or through one dimple 84, and then stop. This can potentiallyavoid cracks spreading through the entire extent of the layer of bonecement and thus destroying the efficacy of the cement.

A further example of an arthroplasty component in accordance with thepresent invention is the patellar implant 300 illustrated in FIGS. 14and 15. The implant 300 has a tray portion 302 with a web surface 304surrounding a plurality of dimples 306. Three posts 308 project from thetray portion 306. When the implant 300 is affixed to a patella, themajority of the bone cement applied between the surface of the patellaand the tray portion 302 flows into the dimples 306 rather than lying onthe web surface 304. Thus, any cracks which might develop in the bonecement are limited to the individual packets of bone cement within thedimples 306.

The present invention also relates to a method of capping a bone inarthroplasty such as shoulder arthroplasty. The joint is first exposedanteriorly so that there is two to three centimeters of space at theanterior side of the joint, between the glenoid bone 100 and the humeralhead (not shown). The glenoid component 10 (FIGS. 5 and 6) is theninserted between the glenoid bone 100 and the humeral head in aposterior direction, as indicated by the arrow 120, with the posteriorlips 24 and 26 of the glenoid component 10 being inserted first. Theglenoid component 10 is inserted until the posterior lips 24 and 26 ofthe glenoid component are posterior to the glenoid bone 100. Theposterior lips 24 and 26 of the glenoid component 10 are slid proximallydown onto the outer side surface 110 of the glenoid bone 100. The hook66 on the posterior lip 24 engages the outer side surface 110 of theglenoid bone 100 and may make a small impression therein.

The glenoid component 10 is then pivoted, in the direction indicated bythe arrow 124, into the capped position shown in FIG. 6. The anteriorlip 22 snaps around the glenoid bone 100 to engage the anterior outerside surface 108 of the glenoid bone 100 at a location spaced from theposterior lips 24 and 26. The lower major side surface 16 of the trayportion 20 is adjacent to or engaged with the articulating surface 106of the glenoid bone 100.

If the glenoid bone 100 is too large in diameter to fit between theanterior and posterior lips of the glenoid component 10, a smallanterior portion of the glenoid bone may be removed as shown at 144,prior to capping with the anterior lip 22. There is desirably a verysnug fit between the glenoid component 10 and the glenoid bone 100. Thiscan be achieved by sizing the glenoid bone 100 and the glenoid component10 so that the surgeon must exert some force to affix the glenoidcomponent to the glenoid bone.

The surgeon then inserts a fastener such as a screw 120 through thescrew opening 52 in the anterior lip 22. The screw 120 seats in the hardcortical bone material at the side of the glenoid bone. In thiscondition, the anterior and posterior tabs and the screw block movementof the tray portion 20 and the entire glenoid component 10 relative tothe bone 100. Because of the secure fixation of the glenoid component10, a central keel is not needed.

As illustrated above, one typically uses a two-material implant (metaland plastic) to obtain different functions of the two differentmaterials at different locations on the implant. A low coefficient offriction is needed at the joint (articulating) surface, because it isbearing on metal. Thus, plastic is chosen for the upper portion orinsert of the implant. Strength and rigidity are needed for the base, incontact with and securing the articulating surface to the bone. Thus,metal is chosen for the base.

The tibial tray 200 (FIGS. 12 and 13), unlike the glenoid component 10illustrated in FIGS. 1-5, is made of only one piece rather than a metalbase and a plastic insert. A glenoid component, or other arthroplastycomponent in accordance with the present invention, may similarly bemade of only one piece of material rather than two pieces bonded orsnapped together. For a glenoid component, this would typically be aplastic material rather than a metal material.

Although all-plastic implants are known and used, applicant has foundthat plastics which are best suited to function as an articulatingsurface are not well suited to function as a base. Polyethylene, forexample, which is suitable as an articulating surface, is too soft andflexible and is not rigid enough over time to present a stable surfacefor bone to bond to. Also, such plastics can fail when screwed intobone.

Thus, all-plastic inserts are always cemented to the bone. However, bonecement does not provide a stable long-term method of fixation. Also, ifbone cement is used, bone ingrowth material can not be used. Boneingrowth material such as hydroxyapatite (HA) or tricalcium phosphate(TCP) will not stick to known bone implant polymers such aspolyethylene. Thus, it is not possible to augment the body's naturalbone growth function at the junction between the implant and the bone.Accordingly, the all-plastic (one-material) implants available today aredeficient in all these regards.

Applicant has found, however, that polyetheretherketone (PEEK) is asuitable material for an all-plastic implant. Applicant has found thatPEEK, when reinforced with fibers (to form a composite material) isstrong enough to replace the metal portion of a typical implant. It canif necessary be screwed into the bone. And, importantly, it is rigidenough and maintains its rigidity over time so that it presents a stablesurface for bone to bond to.

Since composites can be as stiff or as flexible as needed, a portion ofthe PEEK implant can be left unreinforced or only slightly reinforced.Unreinforced PEEK has a coefficient of friction which is acceptably lowfor a joint surface, that is, a coefficient of friction about twice thatof polyethylene. Thus, unreinforced PEEK is suitable for articulation.

Thus, it is possible to provide a one-material insert having a varyingmodulus from proximal to distal--rigid and strong at the bone surface,and smooth at the articulating surface.

Applicant has also found that bone ingrowth material can be bonded toPEEK and will stick. Thus, it is possible to provide an implant ofplastic (specifically, PEEK) and bond a bone ingrowth surface to thelower major side surface (and outer side surfaces also) of the implant.This will make the implant cementless, as the bone ingrowth materialpromotes rapid bone ingrowth and thus substitutes for the cement.

The implant can be made entirely of PEEK reinforced as desired.Alternatively, the implant can be made of another polymer such aspolysulfone or PAEK (polyaryletherketone), reinforced with fibers toform a composite. Suitable fibers include carbon fibers and aramid(Kevlar®) fibers. The implant can also be a base made from PEEKpreferably reinforced with an insert made from another material such aspolyethylene.

The bone ingrowth material can be bonded on as a layer 50-100 micronsthick, or in the form of a mesh or beaded surface with 150-400 micronbead porosity. Known techniques for bonding bone ingrowth material, suchas plasma spraying, can be used, perhaps at a low temperature.

FIGS. 16 and 17 illustrate an arthroplasty component 350 for capping abone such as a glenoid bone or a tibia. The component 350 can beimplanted in the manner described above. The component 350 has a trayportion 352 with an articulating surface 354 and has two tab portions356 and 358 for fixation to cortical bone material.

The component 350 is made of a body 360 of PEEK reinforced with fibers362. The fibers 362 are densest at the proximal portion 364 of thecomponent 350. Thus, the portion 364 of the component 350 is verystrong, strong enough to be attached and stabilized to the bone. Thefibers 362 are less dense at a central portion 366 of the component 350.There are no fibers 362 in the distal portion 368 of the component 350,adjacent the articulating surface 354. Thus, the portion 368 of thecomponent 350 is suitable to provide the articulating surface 354. Thecomponent 350 has a layer of bone ingrowth material 370 bonded to it, inthe manner and for the purposes discussed above.

FIGS. 18 and 19 illustrate another tibial tray in accordance with thepresent invention. The tibial tray 372 includes a plastic insert 374fixed to a metal base 376. The insert 374 has a hollowed outarticulating surface 378. The base has a projecting tab 380 whichextends along the outer side surface of a tibia (shown in phantom). Ascrew hole 382 may be formed in the tab 380 to receive therethrough ascrew (not show) for fixation to the tibia. Additional tabs like the tab380 may be provided, having a fixed pin attached thereto (or formedtherewith), a screw hole, or no additional attachment features.

FIGS. 20-23 illustrate other fixation screws for use in implant fixationin accordance with the present invention. The screw 384 (FIGS. 20-21)has a head 386 with a driver slot 388. A large diameter shank portion390 extends from the head 386. A thread convolution 392 is formed on thelarge diameter shank portion 390. A tapered portion 394 having atruncated conical outer surface 396 extends from the large diametershank portion 390. The tapered portion 394 is smaller in diameter thanthe thread convolution 392. A small diameter shank portion 398 extendsfrom the tapered portion 394. A thread convolution 400 is formed on thesmall diameter shank portion 398. The tapered portion 394 is engageablewith an opening in a keel in an implant (not shown) as in FIGS. 9-11.

The screw 402 (FIGS. 22-23) does not have a radially enlarged head butinstead has a hex driver opening slot 404 in the proximal end surface406 of a constant diameter shank portion 408. A thread convolution 410is formed on the constant diameter shank portion 408. A tapered portion412 extends from the large diameter shank portion 390 and terminates ina pointed distal end 412. The tapered portion 412 is smaller in diameterthan the thread convolution 410. The tapered portion 412 is engageablewith an opening in a keel in an implant (not shown) as in FIGS. 9-11.

From the above description of the invention, those skilled in the artwill perceive improvements, changes and modifications in the invention.Such improvements, changes and modifications within the skill of the artare intended to be covered by the appended claims.

I claim:
 1. A method of positioning an arthroplasty component relativeto a bone, said method comprising the steps of providing an arthroplastycomponent having a tray portion with a first tab extending from one sideof the tray portion and a second tab extending from another side of thetray portion, engaging a first side of the bone with the first tab onthe arthroplasty component, thereafter, pivoting the arthroplastycomponent about a location where the first tab engages the first side ofthe bone, moving the second tab on the arthroplasty component along asecond side of the bone while performing said step of pivoting thearthroplasty component about the location where the first tab engagesthe first side of the bone, and positioning the tray portion of thearthroplasty component over a portion of the bone disposed between thefirst and second sides of the bone while performing said step ofpivoting the arthroplasty component about the location where the firsttab engages the first side of the bone.
 2. A method as set forth inclaim 1 further including the step of moving a fastener through thesecond tab on the arthroplasty component and into the bone with alongitudinal central axis of the fastener extending at an acute angle toa side of the tray portion of the arthroplasty component.
 3. A method ofpositioning an arthroplasty component relative to a bone, said methodcomprising the steps of providing an arthroplasty component having atray portion with a first tab extending from one side of the trayportion, a second tab extending from another side of the tray portionand a keel which extends from the arthroplasty component at a locationbetween the first and second tabs, engaging a first side of the bonewith the first tab on the arthroplasty component, thereafter, pivotingthe arthroplasty component about a location where the first tab engagesthe first side of the bone, moving the second tab on the arthroplastycomponent along a second side of the bone while performing said step ofpivoting the arthroplasty component about the location where the firsttab engages the first side of the bone, moving the keel into the bone atlocation between the first and second sides of the bone while performingsaid step of pivoting the arthroplasty component about the locationwhere the first tab engages the first side of the bone, positioning thetray portion of the arthroplasty component over a portion of the bonedisposed between the first and second sides of the bone while performingsaid step of pivoting the arthroplasty component about the locationwhere the first tab engages the first side of the bone, and moving afastener through the second tab, through a portion of the bone, and intothe keel to retain the arthroplasty component against movement relativeto the bone.
 4. A method of positioning an arthroplasty componentrelative to a bone, said method comprising the steps of providing anarthroplasty component having a tray portion with a first tab extendingfrom one side of the tray portion and a keel which extends from the trayportion of the arthroplasty component, positioning the arthroplastycomponent relative to the bone with the tray portion extending across anend surface on the bone and the first tab extending along a first outerside of the bone which extends transverse to the end surface on thebone, said step of positioning the arthroplasty component relative tothe bone includes moving the keel through the end surface on the boneinto the bone, and applying force to the arthroplasty component urgingthe tray portion of the arthroplasty component toward the end surface onthe bone and urging the first tab toward the first outer side of thebone, said step of applying force to the arthroplasty componentincluding moving a fastener through the first tab and then into the bonealong a path which is skewed at an acute angle to the end surface on thebone, said step of moving the fastener through the first tab and intothe bone along a path which is skewed at an acute angle to the endsurface on the bone includes moving the fastener into the keel.
 5. Amethod of positioning an arthroplasty component relative to a bone, saidmethod comprising the steps of providing an arthroplasty componenthaving a tray portion and a projecting portion extending from the trayportion, positioning the arthroplasty component relative to the bonewith the tray portion extending across an end surface on the bone andthe projecting portion disposed in engagement with the bone andextending transversely to the end surface on the bone, andinterconnecting the arthroplasty component and the bone with a fastener,said step of interconnecting the arthroplasty component and the boneincluding moving the fastener through the projecting portion of thearthroplasty component, moving the fastener through a cortical portionof the bone on a first side of the bone, moving the fastener through acancellous portion of the bone, moving the fastener into a corticalportion of the bone on a second side of the bone, engaging the corticalportion of the bone on the first side of the bone with a first threadconvolution on the fastener, engaging the cortical portion of the boneon the second side of the bone with a second thread convolution on thefastener, and applying force to the arthroplasty component with thefastener during performance of said steps of engaging the corticalportion of the bone on the first side of the bone with a first threadconvolution and engaging the cortical portion of the bone on the secondside of the bone with a second thread convolution to urge the trayportion of the arthroplasty component toward the end surface on thebone, said step of applying force to the arthroplasty componentincluding moving the fastener along a path which is skewed at an acuteangle to the end surface on the bone.
 6. A method as set forth in claim3 wherein said step of moving the fastener into the keel includestransmitting force from the fastener to the keel to urge the trayportion of the arthroplasty component toward the portion of the bonedisposed between the first and second sides of the bone.
 7. A method asset forth in claim 3 wherein said steps of moving the fastener throughthe second tab, through a portion of the bone, and into the keelincludes moving the fastener along a path which is skewed at an acuteangle to a side of the arthroplasty component.
 8. A method as set forthin claim 3 wherein said step of engaging a first side of the boneincludes engaging the first side of the bone with a hook portion of thefirst tab at a location offset from the portion of the bone which isdisposed between the first and second sides of the bone.
 9. A method asset forth in claim 3 wherein said step of moving the second tab on thearthroplasty component along the second side of the bone includesincreasing area of engagement of the second tab with the second side ofthe bone during at least a portion of said step of pivoting thearthroplasty component about a location where the first tab engages thefirst side of the bone.
 10. A method as set forth in claim 3 furtherincluding interconnecting the portion of the bone disposed between thefirst and second sides of the bone and the tray portion of thearthroplasty component with bone cement.
 11. A method as set forth inclaim 7 wherein said step of interconnecting the portion of the bonedisposed between the first and second sides of the bone and the trayportion of the arthroplasty component with bone cement includes fillinga plurality of recesses in a side of the tray portion with bone cementto retard subsequent propagation of cracks through the bone cement. 12.A method as set forth in claim 4 wherein the arthroplasty component hasa second tab which extends from the tray portion, said step ofpositioning the arthroplasty component relative to the bone includingengaging a second side of the bone with the second tab and pivoting thearthroplasty component about a location where the second tab engages thesecond side of the bone.
 13. A method as set forth in claim 4 whereinsaid step of applying force to the arthroplasty component includesapplying force against the keel with the fastener to transmit force fromthe fastener through the keel to the tray portion of the arthroplastycomponent urging the tray portion of the arthroplasty component towardthe end surface on the bone.
 14. A method as set forth in claim 13wherein said step of applying force to the arthroplasty componentincludes applying force against the first tab with the fastener totransmit force from the fastener through the first tab to the trayportion of the arthroplasty component urging the tray portion of thearthroplasty component toward the end surface on the bone.
 15. A methodas set forth in claim 4 wherein said step of moving the fastener throughthe first tab and into the bone along a path which is skewed at an acuteangle to the end surface on the bone includes moving the fastenerthrough a cortical portion of the bone on the first side of the bone andmoving the fastener through the keel on the arthroplasty component and acancellous portion of the bone into a cortical portion of the bone on asecond side of the bone.
 16. A method as set forth in claim 15 whereinsaid step of applying force to the arthroplasty component includesengaging the cortical portion of the bone on the first side of the bonewith a thread convolution and engaging the cortical portion of the boneon the second side of the bone with a thread convolution.
 17. A methodas set forth in claim 4 further including interconnecting the endsurface on the bone and the tray portion of the arthroplasty componentwith bone cement, said step of interconnecting the end surface on thebone and the tray portion of the arthroplasty component with bone cementincludes filling a plurality of recesses in a side of the tray portionwith bone cement to retard subsequent propagation of cracks through thebone cement.
 18. A method as set forth in claim 5 wherein said step ofpositioning the arthroplasty component relative the bone includespivoting the arthroplasty component about a location where the portionof the arthroplasty component engages the second side of the bone andpositioning the tray portion of the arthroplasty component relative tothe end surface of the bone while performing said step of pivoting thearthroplasty component about a location where a portion of thearthroplasty component engages the second side of the bone.
 19. A methodas set forth in claim 5 wherein the projecting portion of thearthroplasty component is a tab which projects from side of the trayportion of the arthroplasty component, said step of positioning thearthroplasty component relative to the bone includes engaging thecortical portion of the bone on the first side of the bone with theprojecting portion of the arthroplasty component, said steps of movingthe fastener through the cortical portion of the bone on the first sideof the bone, moving the fastener through the cancellous portion of thebone, and moving the fastener into a cortical portion of the bone on thesecond side of the bone being performed after moving the fastenerthrough the projecting portion of the arthroplasty component.
 20. Amethod of positioning an arthroplasty component relative to a bone, saidmethod comprising the steps of providing an arthroplasty componenthaving a tray portion with a first tab extending from a first side ofthe tray portion, a second tab extending from a second side of the trayportion and a keel extending from a central portion of the tray portion,said keel extending from the tray portion for a distance which isgreater than a distance which the second tab extends from the trayportion, engaging a first side of the bone with the first tab on thearthroplasty component, thereafter, pivoting the arthroplasty componentabout a location where the first tab engages the first side of the bone,moving the keel into a cancellous portion of the bone while performingsaid step of pivoting the arthroplasty component about the locationwhere the first tab engages the first side of the bone, moving thesecond tab along a second side of the bone while performing said step ofpivoting the arthroplasty component about the location where the firsttab engages the first side of the bone, and, thereafter, moving afastener through the first tab, through a cortical portion of the boneon the first side of the bone and into the keel portion of thearthroplasty component along a path which is skewed at an acute angle tothe tray portion of the bone.
 21. A method as set forth in claim 20further including the steps of engaging the cortical portion of the boneon the first side of the bone with a first thread convolution on thefastener and engaging the cortical portion of the bone on the secondside of the bone with a second thread convolution on the fastener.
 22. Amethod as set forth in claim 20 wherein said step of moving the fastenerinto the keel portion of the arthroplasty component includes engagingthe keel portion of the arthroplasty component with the fastener andtransmitting force from the fastener to the keel portion of thearthroplasty component urging the tray portion of the arthroplastycomponent against the bone.
 23. A method of positioning an arthroplastycomponent relative to a bone, said method comprising the steps ofproviding an arthroplasty component having a tray portion and aprojecting portion extending from the tray portion, the projectingportion of the arthroplasty component is a keel which extends from acentral portion of the tray portion of the arthroplasty component,positioning the arthroplasty component relative to the bone with thetray portion extending across an end surface on the bone and theprojecting portion disposed in engagement with the bone and extendingtransversely to the end surface on the bone, said step of positioningthe arthroplasty component relative to the bone includes positioning thearthroplasty component with the projecting portion extending into acancellous portion of the bone, and interconnecting the arthroplastycomponent and the bone with a fastener, said step of interconnecting thearthroplasty component and the bone including moving the fastenerthrough the projecting portion of the arthroplasty component, moving thefastener through a cortical portion of the bone on a first side of thebone, moving the fastener through a cancellous portion of the bone,moving the fastener into a cortical portion of the bone on a second sideof the bone, engaging the cortical portion of the bone on the first sideof the bone with a first thread convolution on the fastener, andengaging the cortical portion of the bone on the second side of the bonewith a second thread convolution on the fastener, said step of movingthe fastener through the projecting portion of the arthroplastycomponent being performed after moving the fastener through the corticalportion of the bone on the first side of the bone and prior toinitiation of said step of moving the fastener into the cortical portionof the bone on the second side of the bone.
 24. A method of positioningan arthroplasty component relative to a bone, said method comprising thesteps of providing an arthroplasty component having a tray portion witha first tab extending from one side of the tray portion a second tabextending from another side of the tray portion and a projectionextending from the tray portion at a location between the first andsecond tabs, engaging a first side of the bone with the first tab on thearthroplasty component, thereafter, pivoting the arthroplasty componentabout a location where the first tab engages the first side of the bone,moving the projection from the tray portion into the bone at a locationbetween the first side of the bone and a second side of the bone whileperforming said step of pivoting the arthroplasty component about thelocation where the first tab engages the first side of the bone, movingthe second tab on the arthroplasty component along the second side ofthe bone while performing said step of pivoting the arthroplastycomponent about the location where the first tab engages the first sideof the bone, and positioning the tray portion of the arthroplastycomponent over a portion of the bone disposed between the first andsecond sides of the bone while performing said step of pivoting thearthroplasty component about the location where the first tab engagesthe first side of the bone.
 25. A method as set forth in claim 24further including the step of moving a fastener through at least one ofthe tabs on the arthroplasty component and into the projecting portionof arthroplasty component with a longitudinal central axis of thefastener extending at an acute angle to a side of the tray portion ofthe arthroplasty component.
 26. A method of positioning an arthroplastycomponent relative to a bone, said method comprising the steps ofproviding an arthroplasty component having a tray portion with a firsttab extending from one side of the tray portion and a second tabextending from another side of the tray portion, engaging a first sideof the bone with the first tab on the arthroplasty component,thereafter, pivoting the arthroplasty component about a location wherethe first tab engages the first side of the bone, moving the second tabon the arthroplasty component along a second side of the bone whileperforming said step of pivoting the arthroplasty component about thelocation where the first tab engages the first side of the bone,positioning the tray portion of the arthroplasty component over aportion of the bone disposed between the first and second sides of thebone while performing said step of pivoting the arthroplasty componentabout the location where the first tab engages the first side of thebone, and moving a fastener through the second tab on the arthroplastycomponent, through a cortical portion of the bone on the second side ofthe bone, through a cancellous portion of the bone located between thefirst and second sides of the bone and into engagement with a corticalportion of the bone on the first side of the bone.
 27. A method ofpositioning an arthroplasty component relative to a bone, said methodcomprising the steps of providing an arthroplasty component having atray portion with a first tab extending from one side of the trayportion, a second tab extending from another side of the tray portion,and a keel which extends from the tray portion at a location between thefirst and second tabs, engaging a first side of the bone with the firsttab on the arthroplasty component, thereafter, pivoting the arthroplastycomponent about a location where the first tab engages the first side ofthe bone, moving the keel into the bone at a location between the firstand second sides of the bone while performing said step of pivoting thearthroplasty component about the location where the first tab engagesthe first side of the bone, moving the second tab on the arthroplastycomponent along a second side of the bone while performing said step ofpivoting the arthroplasty component about the location where the firsttab engages the first side of the bone, and positioning the tray portionof the arthroplasty component over a portion of the bone disposedbetween the first and second sides of the bone while performing saidstep of pivoting the arthroplasty component about the location where thefirst tab engages the first side of the bone.
 28. A method ofpositioning an arthroplasty component relative to a bone, said methodcomprising the steps of providing an arthroplasty component having atray portion with a first tab extending from one side of the trayportion and a second tab extending from another side of the trayportion, the first tab having a first portion which is connected withthe tray portion and extends transverse to the tray portion in adirection which is generally parallel to a central axis of the trayportion and a second portion which extends transverse to the firstportion in a direction toward the central axis of the tray portion,engaging a first side of the bone with an end of the second portion ofthe first tab on the arthroplasty component, thereafter, pivoting thearthroplasty component about a location where the end of the secondportion of the first tab engages the first side of the bone, said stepof pivoting the arthroplasty component being at least partiallyperformed with a portion of the bone disposed between the tray portionand the second portion of the first tab, moving the second tab on thearthroplasty component along a second side of the bone while performingsaid step of pivoting the arthroplasty component about the locationwhere the second portion of the first tab engages the first side of thebone, and positioning the tray portion of the arthroplasty componentover a portion of the bone disposed between the first and second sidesof the bone while performing said step of pivoting the arthroplastycomponent about the location where the second portion of the first tabengages the first side of the bone, said step of positioning the trayportion of the arthroplasty component over a portion of the boneincludes positioning the tray portion of the arthroplasty component overthe portion of the bone disposed between the tray portion and the secondportion of the first tab.
 29. A method as set forth in claim 28 furtherincluding the step of moving a fastener through the second tab on thearthroplasty component and into the bone with a longitudinal centralaxis of the fastener extending at an acute angle to a side of the trayportion of the arthroplasty component.
 30. A method as set forth inclaim 28 further including the steps of moving a fastener through thesecond tab on the arthroplasty component, through a cortical portion ofthe bone on the second side of the bone, through a cancellous portion ofthe bone located between the first and second sides of the bone and intoengagement with a cortical portion of the bone on the second side of thebone.
 31. A method as set forth in claim 28 wherein the arthroplastycomponent has a keel which extends from the tray portion of thearthroplasty component at a location between the first and second tabs,said method further including the step of moving the keel into the boneat location between the first and second sides of the bone whileperforming said step of pivoting the arthroplasty component about thelocation where the first tab engages the first side of the bone.
 32. Amethod as set forth in claim 31 further including the steps of moving afastener through the second tab, through a portion of the bone, and intothe keel to retain the arthroplasty component against movement relativeto the bone.
 33. A method as set forth in claim 31 further including thestep of transmitting force from a fastener to the keel to urge the trayportion of the arthroplasty component toward the portion of the bonedisposed between the first and second sides of the bone.
 34. A method asset forth in claim 31 further including the step of moving a fastenerinto the keel along a path which is skewed at an acute angle to a sideof the arthroplasty component.
 35. A method as set forth in claim 28wherein said step of moving the second tab on the arthroplasty componentalong the second side of the bone includes increasing area of engagementof the second tab with the second side of the bone during at least aportion of said step of pivoting the arthroplasty component about alocation where the second portion of the first tab engages the firstside of the bone.
 36. A method as set forth in claim 28 furtherincluding interconnecting the portion of the bone disposed between thefirst and second sides of the bone and the tray portion of thearthroplasty component with bone cement.
 37. A method as set forth inclaim 36 wherein said step of interconnecting the portion of the bonedisposed between the first and second sides of the bone and the trayportion of the arthroplasty component with bone cement includes fillinga plurality of recesses in a side of the tray portion with bone cementto retard subsequent propagation of cracks through the bone cement.